Disk Of NGC Research Articles

Disk Mass Densities in Edge-On Spiral Galaxies

Very Large Array (VLA) observations of the neutral hydrogen (HI) gas in two nearby edge-on spirals (NGC 4565 and NGC 891) successfully resolve the thickness of the gas layers in both disks over a wide range in radii. The combination of B, C, and D array data produces a 4 arcsec (approx. 200 pc) beam and 21 km s(exp -1) velocity resolution, combined with sensitivity to structures as large as 18 arcmin (approx. 54 kpc). These observations directly constrain the mid-plane disk mass densities, under the assumption of an equilibrium between the thermal pressure of the gas and the gravitational attraction of the disk. The results of a preliminary analysis are given regarding the z-velocity dispersion of the gas, the mass-to-light ratio of the disk in NGC 4565, and the roles of atomic and molecular gases. The data also allow a detailed study of the HI in these galaxies; in general their brightness temperature distributions seem similar to that in the Milky Way. Both galaxies show asymmetric HI extensions beyond the optical disk. In NGC 4565 the extension is a surprisingly abrupt warp, which may bend back to parallel the galactic plane; the velocity structure implies the warp is continuous around the disk.

The infrared structure and the origin of the starburst disk in NGC 1068

A detailed map of the extranuclear IR emission in the central 4 kpc of the luminous Seyfert galaxy NGC 1068 is presented. The relationship of the IR emission with low-excitation, visible H II regions implies that the IR luminosity is powered by recent star formation. The observations show that the star formation is distributed across the central 3.5 kpc primarily in two very extended complexes, one located to the north of the nucleus and the other to the southwest. These two complexes coincide with the two dominant CO features. It is shown that there are two inner Lindblad resonances which occur near the ends of the bar which approximately bound the IR-luminous star-forming regions, the CO complexes, and the visually bright spiral arms. It is proposed that the starburst results from a bar-driven density wave which also includes the effects of shock focusing.

The z-structure of the disc of NGC 3115

Les observations photometriques du disque de la galaxie SO NGC 3115 presentees par Capaccioli M., Held E.V. et Nieto J.L. (1987, Astr. J., 94) sont analysees dans le but de donner une interpretation dynamique de la structure du disque

CCD surface photometry of the bright elliptical galaxies NGC 720, NGC 1052, and NGC 4697

view Abstract Citations (39) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CCD Surface Photometry of the Bright Elliptical Galaxies NGC 720, NGC 1052, and NGC 4697 Jedrzejewski, Robert I. ; Davies, Roger L. ; Illingworth, Garth D. Abstract R band CCD frames of three elliptical galaxies of similar luminosity and flattening have been analyzed under fairly good seeing conditions, and the radial variation of surface brightness, ellipticity, position angle, and cos (4 theta) component, which measures the degree to which the isophotes may be 'boxy' or 'pointed', has been determined. Comparison with other modern observations and between independent frames obtained for this study reveals that the results are accurate and repeatable. It is found that although the galaxies have similar global properties, such as luminosity and flattening, the detailed structure, namely core size, isophote twists, and cos (4 theta) component, differs markedly. Evidence is found for a weak disk in NGC 4697, but it is argued that this does not contribute significantly to the relatively rapid major-axis rotation seen in this object. Publication: The Astronomical Journal Pub Date: December 1987 DOI: 10.1086/114584 Bibcode: 1987AJ.....94.1508J Keywords: Astronomical Spectroscopy; Brightness Distribution; Charge Coupled Devices; Elliptical Galaxies; Radial Distribution; Disk Galaxies; Galactic Structure; Spectral Bands; Spectrum Analysis; Astronomy; GALAXIES: GENERAL full text sources ADS | data products SIMBAD (6) NED (4)

Molecules in galaxies. II - The disk of NGC 4565

Emission in the J = 1-0 line of CO has been mapped along the major axis of the large edge-on Sb galaxy NGC 4565. The shape of the CO distribution is very similar to that of the radio continuum emission, and of the disk light. The CO emission is much more centrally peaked than is the H I, but the total (H I+H2) gas surface density may have a smooth radial distribution. The total molecular hydrogen mass is similar to that of the H I. The asymmetry seen in the H I emission in this galaxy is also seen in the CO emission, implying that the ''lopsidedness'' of this galaxy is present at relatively small radii and high disk densities.

IUE observations of a starburst disk and the detectability of high redshift galaxies

The high-surface-brightness inner disk of NGC 1068 has been observed with the IUE to determine the ultraviolet spectrum and surface brightness profile. This disk is explained by an intense starburst, requiring formation of 1-2 massive stars/yr, so it is a good prototype for seeking at early epochs in the universe. Calculations of isophotal diameter as a function of redshift are presented. It is found that this disk could be resolved to z of about 0.3 from the ground or to z of about 2.0 with the Hubble Space Telescope. For z greater than about 1.3, such a disk is more easily observable than a large, normal galaxy.